He causes himself to be represented on his Coins, and in his Portraits, in the Attitude of Prayer
How deeply his soul was impressed by the power of divine faith may be understood from the circumstance that he directed his likeness to be stamped on the golden coin of the empire with the eyes uplifted as in the posture of prayer to God: and this money became current throughout the Roman world. His portrait also at full length was placed over the entrance gates of the palaces in some cities, the eyes upraised to heaven, and the hands outspread as if in prayer.
Source: Life of Constantine (New Advent)